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Piston opening

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Piston opening

Unread postAuthor: squeaks » Sun Nov 26, 2006 11:28 am

Can someone explain this to me.
Minimum Required Opening Distance for a Coaxial Piston Valve

Abarrel=pi*r^2
Avalve=2pi*2r*X(open)
Abarrel=Avalve
pi*r^2=4piRX(open)
X(open)=R/4

I understand the area calculation for the barrel, that's just a circle. I don't understand the area for the valve though. What kind of shape is that calculating for? Someone please help.
Thanks
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Re: Piston opening

Unread postAuthor: SpudBlaster15 » Sun Nov 26, 2006 4:56 pm

squeaks wrote:I don't understand the area for the valve though. What kind of shape is that calculating for?


Look at the formula. Isnt it obvious?

Avalve=2pi*2r*X(open)


"Avalve" is the area the valve must uncover when it opens in order for proper flow. The variable that you are calculating, X, is the distance the valve must travel in order to do so.
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Unread postAuthor: squeaks » Sun Nov 26, 2006 5:28 pm

No, no no. I'm want to know what shape that is that he is getting the formula from. I know I'm calculating how far the valve is opening.
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Unread postAuthor: SpudBlaster15 » Sun Nov 26, 2006 5:39 pm

Fine, I will be more specific.

"Avalve" is a cylindrical lateral surface area calculation. The X variable is the height of said cylinder, and thus represents the distance the valve is required to move. Keep in mind that lateral surface area is the surface area of an object, minus the top and bottom.

The overall calculation states basic logic. The lateral area uncovered by the valve must equal the area of the barrel opening for full flow.
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